Environmental Engineering Reference
In-Depth Information
I
, Current
+
Measuring Magnetic Flux Density,
B
Gauss Meter
0.5 cm
1.0 cm
1.5 cm
r
a
FIGURE 6.1
Characterization of a magnetic energy source based on Ampere's law.
the power cable and the radius distance
r
a
between the measurement point
and the centre of the conductor, it is possible to determine the magnetic field
lines that best describe the magnetic energy generated by the current flowing
in the power line.
The second part of the characterization process is to determine the volt-
age induced by the toroid-based magnetic energy harvester, constructed by
physically winding
N
turns of copper wires on a circular ring-shaped ferrite
magnetic core as shown in
Figure 6.2
. When the current-carrying power cable
is laid through the centre of the ferrite core as illustrated in
Figure 6.3
, mag-
netic field lines are generated. These magnetic field lines circulate around the
ferrite core and its copper winding and an AC (alternating current) voltage
is induced. The induced voltage is proportional to the rate of change in the
number of flux lines enclosed by the loop per unit time and the number of
winding turns
N
in the loop. In other words, the induced voltage is related
FIGURE 6.2
To p view of ferrite core windings.
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